1. Field of the Invention
This invention relates to linear motors, and more particularly relates to a radial pole linear reluctance motor configuration having a smooth double-helix stator shaft and a smooth laminated armature made up as a stack of alternate radial pole laminations and spacer laminations separated by tolerance-compensating spacing cement layers, the resulting configuration allowing a balanced flux path across the stator shaft, and allowing smooth sliding contact of armature and stator shaft within the electromagnetically active envelope.
2. Related Prior Art
A large number of linear reluctance motors have been developed, including coupled-phase and uncoupled-phase variable reluctance designs as well as hybrid permanent-magnet designs. While these motors provide good performance, they have not achieved widespread commercial application. The relatively large cardinal step size of typical linear stepping motors, and the prohibitive cost of many closed-loop control schemes, have limited their use in high-resolution, highly-controllable actuator motion applications such as printers, plotters, robots, and disk drives.
Recently, however, the emergence of low-cost microcontrollers and the new generation of `smart-power` devices has made feasible the use of sophisticated commutation and control schemes. These sophisticated control schemes eliminate many of the drawbacks of a conventional stepping motor. The stepper motor, for example, may be controlled as if it were a brushless DC servomotor.
Another reason for the limited use of linear variable-reluctance (VR) motors has been their high manufacturing costs relative to costs for rotary VR motors. The cost differential results from design details, such as shaft bearings requiring accurate alignment, and such as complex laminated armature/stator shafts, as well as higher production volumes of many rotary VR motors.